Some people were sharing that the kiosks at the airports were also not working. A "not in service" Tweets were coming from airports across the country. One traveler said that there were almost 200 people "looking for answers" in Austin, Texas.

American Airlines did not tweet out a reason for the outage while hundreds of complaints rolled in from frustrated customers. Customers were concerned about missing flights without access to boarding passes and flight information.

"We experienced a brief technical issue impacting several systems including aa.com, our mobile app and self-service kiosks at airports. The issue has been resolved and we apologize to our customers for the inconvenience," American Airlines said in a statement to Newsweek.

A 2013 computer glitch grounded American Airlines flights across the country for the better part of the day. The outage lasted hours during that incident and caused delays and cancellations for that entire time, CNN reported.

This story was updated to include further information about the outage and a statement from American Airlines.

american airlines check in

Passengers check in for American Airlines flights at O'Hare International Airport on November 30, 2017 in Chicago, Illinois. The online check-in system was down Wednesday. Scott Olson/Getty Images